Human Exposure to Hydrogen Sulfide

Hydrogen Sulfide’s (H2S) main route in the human body is through inhalation and can potentially damage any of the body’s physiological systems: respiratory, cardiovascular neurological, ocular, metabolic, and the reproductive system. No known carcinogenic properties have been reported.

Respiratory Effects:

Through inhalation, exposure to hydrogen sulfide that is greater than or equal to 700 mg hydrogen sulfide/m3 can result in acute respiratory failure. The effects on the respiratory system are:

Non-cardiogenic pulmonary edema

the alveoli is where gas exchange between oxygen and carbon dioxide occur

hydrogen sulfide causes inflammation and compromises the alveoli, having the alveoli fill up with excess liquid from the capillaries, making gas exchange extremely difficult and inhibiting oxygenation for the body to function

untreated non-cardiogenic pulmonary edema will eventually cause hypoxia, low levels of oxygen in the blood

“non-cardiogenic” means the pulmonary (in relation to the lungs) edema is not related to heart failure

Neurological Effects:

Neurological effects may be acute or chronic, having the potential to be permanent depending on the severity of exposure. Symptoms may include:

Nausea

An uncomfortable feeling in the stomach that can cause vomiting

Headaches

Pain and discomfort within the back of the head, upper neck, front of the head, or sides of the head

Delirium

State of confusion and the inability to function psychologically

Psychosis

It may include auditory or visual hallucinations, disorientation, paranoia, and anxiety

Poor Memory

The inability to encode, retrieve, and recall certain past or recent events

Neurobiological changes

Change in physiological functioning of the brain and can cause structural, behavioural, and personality changes

Olfactory Paralysis

The loss of ability to distinguish between odours and perceive such odours

Tremors

Involuntary movements of the muscles that can affect any part of the body

Abnormal electrical signals between neuron cells

Convulsions

Involuntary contractions of the muscles; shaking uncontrollably

Lethargy

extreme fatigue, feeling sleepy

Insomnia

that ability of having trouble falling asleep or stay asleep in a normal cycle

Ataxia

affects the cerebellum, coordination and the ability of movement is compromised

Cerebral atrophy

The process of death and re-absorption of cells causing deterioration of brain cells, disrupting the physiological equilibrium of the cerebral system

Ocular Effects:

Depending on the level of exposure to the eye, a variety of symptoms may occur having extreme irritation to the eye as the most common symptom. Other symptoms may include:

Photophobia

Having an extreme case of sensitivity towards light coming from any form of light source; can cause headaches, nausea and other symptoms

Keratoconjunctivitis

Inflammation of the cornea and conjunctiva

Blepharospasm

Muscle spasms that control the eyelid which causes uncontrollable blinking or complete inability to open the eye lids

Lacrimation

Excess tears shed than normal

Metabolic Effects:

Hydrogen sulfide can impair the body’s metabolic system in relation to how the body uses oxygen to aid in physiological functioning. Impairment in the metabolic system can cause:

Increased blood lactate concentration

Is an indicator of having the body going through shock

Associated with tachycardia, hypotension, cold and clammy skin

Decrease in oxygen uptake

Can lead to hypoxia

Hydrogen sulfide can cause acidosis (decrease pH levels in the blood) which changes the structure of haemoglobin, inhibiting the protein from binding with oxygen within the capillaries of the alveoli, preventing oxygen distribution towards the entire body

Decrease in skeletal muscle citrate synthase activity

Decrease activity within the aerobic and mitochondrial activity within cells, particularly the muscle cells

Can cause convulsions

Switch from aerobic to anaerobic metabolism

Aerobic Metabolism – uses oxygen to convert nutrients such as carbohydrates, fats, and protein into ATP (adenosine triphosphate), a type of energy “currency” for the body

Anaerobic Metabolism – also known as glycolysis, is the process of producing ATP directly and only from carbohydrates without the use of oxygen; by-product is lactic acid – too high of a concentration of lactic acid will cause pain and discomfort

Reproductive Effects:

With many physiological abnormalities that hydrogen sulfide incurs in the body, it is reasonable that women who are pregnant have an increased risk of having an abortion/miscarriage due to the physiological irregularities. Defects and other abnormalities may also result in the fetus.